Sun now setting about 75 seconds earlier every day

The Time of Sunset changes most rapidly this time of the year. This is mainly because the sun is swinging rapidly south along the ecliptic (its apparent path through the background stars). From the latitude of San Diego, the sun is now setting about 75 seconds earlier every day (equivalent to about 9 minutes earlier per week), and its setting position along the horizon shifts southward about 1/2 degree per day.

The New Moon returned to the evening sky Monday, September 6. This week, the thickened crescent moon will lie in a favorable southerly position for evening telescopic viewing. September evenings in San Diego are often a perfect time to turn a telescope on the moon and note its hundreds of visible craters. Calmer weather conditions this time of year tend to minimize atmospheric turbulence over San Diego’s coastal and inland areas, and that contributes to crisper telescopic views.

Now catch the more obvious crescent Moon paired with white-light Venus low in the west-southwest in twilight. They’ll be 4° apart for North America. Can you make out Spica below them? Look left of the thick crescent Moon for the head stars of Scorpius, then orange Antares. Halfway between the Moon and Antares is the brightest of the head stars, the long-term eruptive variable Delta Scorpii. It’s been holding fairly steady at magnitude 1.8 since 2010.

The above comes from the Outdoors listings in the Reader compiled by Jerry Schad, author of Afoot & Afield in San Diego County. Schad died in 2011. Planet information from SkyandTelescope.org.